I am currently working on angiogenesis in zebrafish embryos and the technique I use to visualize the vessels is EAP staining using NBT/BCIP. Earlier the method was working for me. This is not working these days. I tried changing all the possible changes. Tried using new NBT/BCIP stock (Conc 0.42mg NBT and 0.51mg BCIP) equlibration time about 1 hr. But I am unable to get the method work. Please suggest me some possible changes I can make.